AT&T Michigan in Ann Arbor, MI
These numbers are located in the city of Ann Arbor part of Washtenaw county. There are a few other subcodes that cover this area as well so take care not to confuse them.
Washtenaw county is situated in Michigan and operates ET (UTC -05:00) time. This number group covers the 48104, 48106, 48105, & 48107 zip codes.